The present invention relates to capacitor structures, and particularly to capacitor structures having interdigitated conductive lines, and methods of manufacturing the same.
Prior art back-end-of-line (BEOL) metal capacitors employ conductive lines embedded in a dielectric material layer. The conductive lines are formed as metal lines filling line trenches in the dielectric material layer at the same time when other metal lines for metal interconnect structures are formed. The distance between the conductive lines is typically a critical dimension, i.e., the smallest dimension that may be printed by lithographic methods. Because such BEOL metal capacitors are formed in the same processing steps that are employed to form other metal interconnect structures, such BEOL metal capacitors may be manufactured without incurring an additional processing cost.
Because of the relatively great separation distance between the metal lines, such a BEOL metal capacitor requires a relatively large area. While a smaller area for such BEOL metal capacitors is desirable, the line width of the conductive lines may not be reduced without increasing the risk for electrical shorts between the metal vias, which electrically connect the conductive lines to conductive structures in different levels, and other conductive structures located nearby. Particularly, metal vias tend to be formed with a wider diameter in an upper portion relative to a lower portion, thereby increasing the area of the metal via and consequently increasing the probability of electrical shorts when a metal via is located directly underneath a metal line.
Because the presence of a metal via directly underneath a metal line tends to widen the physical width of the metal line and increase the possibility of electrical shorts between a metal via and adjoining conductive structures, prior art BEOL metal capacitors face a limit in scaling triggered by the presence of the metal vias.